The present invention relates to a fault point location system. More particularly, the present embodiment relates to a fault point location system by which fault points can be quickly located at the time of a fault along a transmission and distribution line. Additionally, the present other embodiments relate to a fault point location system by which fault points can be identified on a map for which a transmission and distribution line map is automatically prepared in response to relocation and extension of the transmission and distribution line.
Heretofore, map information with power transmission lines and distribution lines (hereinafter designated xe2x80x9ctransmission and distribution linexe2x80x9d or xe2x80x9cTD linexe2x80x9d for both lines) illustrated on a map has been available.
In addition, a method has been developed for locating a fault according to a difference in the time of surge detection at both ends of a straight TD line with no branch in the case where a fault occurs along the line. (Japanese Patent Publication No.Sho 63 (1988)-51274, etc.)
However, said map information with TD lines illustrated on a map has not been updated in real time in response to frequent relocation or extension of actual TD lines. For this reason, in an emergency case, quick action sometimes could not be taken due to a difference between a TD line map and actual TD line.
Moreover, although such a fault point identifying method as disclosed in Japanese Patent Publication No.Sho 63 (1988)-51274, which allowed for identifying the distance along a TD line from both ends thereof, wherein a surge was detected, precise location of the fault for fault recovery could not be determined on a map since the actual TD line was placed in a meandering fashion.
Still moreover, although an approximate point of a fault could be identified on a map according to the distance on the TD line from both ends thereof where a surge was detected even on a winding TD line, an actual TD line is not one line but arranged with a plurality of branches, and therefore, such a fault point identifying method as disclosed in Japanese Patent Publication No.Sho 63 (1988)-51274 cannot be applied as it is for locating fault points.
An object of the present invention is to provide a fault point location system by which a fault point can be quickly located and identified on a TD line map for solving the above mentioned problems. Another object of the present invention is to provide a fault point location system that allows for automatically preparing a TD line map in response to relocation and extension of TD lines, and locates a fault point on a map in the case of an occurrence of a fault on a TD line.
A fault point location system of a first embodiment is a fault point location system comprising:
substations 1 installed along TD lines for sending information along said TD lines to a master station 2, and the master station 2 for locating fault points on the basis of the information sent by said substations 1;
characterized in that
said substation 1 has a clock function, receives radio waves from a GPS satellite to identify the current time the GPS has, is able to synchronize the current time said GPS has with the self current time, detects a surge current or surge voltage of the TD line along which said substation 1 is installed to identify a surge detection time, the time at which said surge current or surge voltage is detected, recognizes the polarity of said surge current, and then sends said surge detection time and information on said polarity to said master station 2 via a communication network; and
said master station 2 receives said surge detection time and information on said polarity, which are transmitted from said substation 1 via the communication network,
identifies a section with no branch as the section of occurrence of a fault on the basis of information on said polarity of each substation 1, and
identifies the point of occurrence of a fault along the TD line on the basis of a difference in the time of detection of said surge detected by substations 1 at both ends of said fault section, and the length of said fault section along the TD line.
In the foregoing, the xe2x80x9cGPS radio wavesxe2x80x9d are radio waves a satellite emits in the xe2x80x9cGPSxe2x80x9d. Additionally, the xe2x80x9cGPSxe2x80x9d is an abbreviation for the xe2x80x9cGlobal Positioning Systemxe2x80x9d, a system for determining a position on the basis of differences in time when receiving radio waves from a plurality of satellites.
In the foregoing, the xe2x80x9cfault sectionxe2x80x9d is a section with no branch that is identified as a section of occurrence of a fault.
A fault point location system of a second embodiment has, in the fault point location system according to embodiment 1:
said substation 1 comprising a GPS receiving means 11, a time measuring means 12, a surge detection means 13, and a surge information transmitting means 14b, wherein
said GPS receiving means 11 receives GPS radio waves from satellites for identifying the current time the GPS has to send the current time said GPS has to said time measuring means 12,
said time measuring means 12 has a clock function for synchronizing the current time said GPS has from said GPS receiving means 11 with the current time of said substation 1 and then sends information on said current time of said substation 1 to the surge detection means 13,
said surge detection means 13 detects a surge current or surge voltage of a TD line along which said substation 1 is installed, identifies the time of surge detection time at which said surge detection signal is received on the basis of information on the time sent by said time measuring means 12, also recognizes a polarity of said surge current, and transmits said surge detection time and said polarity to said surge information transmitting means 14b, and
said surge information transmitting means 14b sends said surge detection time and said information on polarity to said master station 2 via a communication network; and
said master station 2 comprising a substation surge information receiving means 21b, a fault section identifying means 23b, and a fault location identifing means 23c, wherein
said substation surge information receiving means 21b receives said surge detection time sent by said surge information transmitting means 14b and said information on polarity via a communication network, then sends said information on polarity to said fault section identifying means 23b, and sends said surge detection time to fault location identifying means 23c, 
said fault section identifying means 23b identifies a section with no branch as a section of occurrence of a fault on the basis of said information on polarity of each substation 1 and sends said section as a fault section to said fault location identifying means 23c, and
said fault location identifying means 23c identifies a point of occurrence of a fault along a TD line on the basis of a difference in said surge detection time of substations 1 at both ends of said fault section and the length of the TD line of said fault section.
In the foregoing, assume the xe2x80x9cpolarityxe2x80x9d of a surge current xe2x80x9cpositive (+)xe2x80x9d for ground fault current flowing from a source-side to a load-side and xe2x80x9cnegative (xe2x88x92)xe2x80x9d for ground fault current flowing from the load-side to the source-side.
A fault point location system of a third and a seventh embodiment in the fault point location system according to embodiment 2 or 6, wherein, in accordance with said surge detection time t1 detected at one of the substations at both ends of said fault section, said surge detection time t2 of the other substation, surge propagation velocity v, and length L of the TD line of the section of said fault has occurred, said fault location identifying means determines distance L1 on a TD line from one of the substations to the location of the fault along the TD line is determined by equation L1=(L+(t1xe2x88x92t2)xc3x97v)/2.
A fault point location system of a fourth and an eighth embodiment in the fault point location system according to embodiment 3 or 7, allows said fault location identifying means to identify sections of occurrence of a fault through the procedures wherein:
1. Select one TD line that extends from a power source,
2. Compare data of a surge rising polarity of a substation with that of its neighboring substation along said TD line selected,
3. If there is a substation of a polarity opposite to its neighboring substation and the section with the substations located at the ends of the section has no branch, decide that the section is xe2x80x9cthe section with a faultxe2x80x9d,
4. If there is a substation of a polarity opposite to its neighboring substation and the section with said substations located at the ends of the section has a branch, compare the surge rising polarity data of the most upstream substation among the substations of the spur TD line with the surge rising polarity data of the upstream substation among substations which have a polarity opposite to their neighboring substation of the trunk TD line,
5. If the polarity of the most upstream substation among the substations of said spur TD line is opposite to the polarity of the upstream substation among substations which have a polarity opposite to their neighboring substation of said trunk TD line, decide that the section ranging from the most upstream substation among the substations of said spur TD line through the upstream substation among substations which have a polarity opposite to their neighboring substation of said trunk TD line to the downstream substation among substations which have a polarity opposite to their neighboring substation of said trunk TD line is a xe2x80x9csection of a faultxe2x80x9d,
6. If the polarity of the most upstream substation among the substations of said spur TD line is the same as the polarity of the upstream substation among substations which have a polarity opposite to their neighboring substation of said trunk TD line, select one TD line out of said spur TD lines to replace said xe2x80x9cone TD line selectedxe2x80x9d with the TD line out of said spur TD lines and perform the procedures from the foregoing 2.
In the foregoing, xe2x80x9cto select one TD linexe2x80x9d is defined for a TD line with no branch as to select the TD line, and for a TD line with a branch along the line as to select a series of TD lines with no branch out of TD lines with branches along the lines thereof.
In addition, the xe2x80x9cspur TD linexe2x80x9d is a TD line branched from xe2x80x9cone TD line selectedxe2x80x9d. The xe2x80x9ctrunk TD linexe2x80x9d is xe2x80x9cone TD line selectedxe2x80x9d. These xe2x80x9cspurxe2x80x9d and xe2x80x9ctrunkxe2x80x9d indicates, however, only a relative relationship of TD lines to be branched. Accordingly, the xe2x80x9ctrunk TD linexe2x80x9d is not always connected directly to a power station.
Moreover, the xe2x80x9cupstreamxe2x80x9d indicates source-side, while xe2x80x9cdownstreamxe2x80x9d indicates load-side.
A fault point location system of a fifth embodiment comprising:
substations 1 which are installed along a TD line to transmit information on said TD line to a master station 2, and
a master station 2 which prepares TD line map information on the basis of information from said substations 1 to locate faults;
said fault point location system characterized in that
said substation 1 receives GPS radio waves from a satellite for identifying its own position on the basis of said GPS radio waves and then transmits information on said own position to said master station 2 via communication networks,
further, said master station 2 receives the information on the position of said substation 1 sent by said substation 1 via communication networks for preparing TD line map information which has TD lines illustrated on a map on the basis of map information on a region where each substation is installed and information on the position of said substations,
and then outputs said TD line map information,
said substation 1 has a clock function, receives radio waves from a GPS satellite to identify the current time of the GPS, is able to synchronize the current time of said GPS with the self current time, detects a surge current or surge voltage of the TD line along which said substation 1 is installed to identify a surge detection time, the time at which said surge current or surge voltage is detected, recognizes the polarity of said surge current, and then sends said surge detection time and information on said polarity to said master station 2 via a communication network, and
said master station 2 receives said surge detection time and information on said polarity, which are transmitted from said substation 1 via the communication network,
identifies a section with no branch as the section of an occurrence of a fault on the basis of information on said polarity of each substation 1,
identifies the point of an occurrence of a fault along the TD line on the basis of a difference in the time of detection of said surge detected by substations 1 at both ends of said fault section, and the length of said fault section along the TD line, identifies said point of occurrence of a fault along the TD line on a TD line of said TD line map information, re-prepares the TD line map information in consideration of said identified information at the point of occurrence of a fault, and outputs said re-prepared TD line map information.
A fault point location system of a sixth embodiment in the fault point location system, according to embodiment 5, wherein
said substation 1 comprises a GPS receiving means 11, a time measuring means 12, a surge detection means 13, a self-position information transmitting means 14a, and a surge information transmitting means 14b; 
said master station 2 comprises a substation location information receiving means 21a, a substation surge information receiving means 21b, a map information storage means 22, a TD line map information preparing means 23a, a fault section identifying means 23b, a fault location identifying means 23c, and a TD line map information output means 24;
said GPS receiving means 11 receives GPS radio waves from a satellite for identifying its own position on the basis of said GPS radio waves and then transmits information on said own position to said self-position information transmitting means 14a; 
said self-position information transmitting means 14a transmits information on said own position to said master station 2 via communication networks;
said substation location information receiving means 21a receives the information on the position of said substation 1 sent by said self-position information transmitting means 14a via communication networks to transmit the information on the position of said substation 1 to said TD line map information preparing means 23a; 
said map information storage means 22 is able to provide map information on a region where each substation is installed for said TD line map information preparing means 23a; 
said TD line map information preparing means 23a receives said map information from said map information storage means 22 for preparing TD line map information which has TD lines illustrated on a map on the basis of said map information and the information on the position of said substations which was received from said substation location information receiving means 21a to transmit said TD line map information to said TD line map information output means 24;
said TD line map information output means 24 outputs said TD line map information;
further, said GPS receiving means 11 receives GPS radio waves from a satellite to identify the current time of the GPS and transmits said current time of the GPS to said time measuring means 12;
said time measuring means 12 has a clock function, is able to synchronize the current time said GPS has sent by said GPS receiving means 11 with the self current time, and transmits said self current time information to the surge detection means 13;
said surge detection means 13 detects a surge current or surge voltage of the TD line along which said substation 1 is installed to identify a surge detection time, the time at which said surge current or surge voltage signal is received, on the basis of information on the time from said time measuring means 12, recognizes the polarity of said surge current, and then sends said surge detection time and information on said polarity to said surge information transmitting means 14b; 
said surge information transmitting means 14b sends said surge detection time and information on said polarity to said master station 2 via a communication network;
said substation surge information receiving means 21b receives said surge detection time and said information on polarity, which are transmitted from said surge information transmitting means 14b, via the communication network, transmits said information on polarity to said fault section identifying means 23b, and transmits said surge detection time to said fault location identifying means 23c; 
said fault section identifying means 23b identifies a section with no branch as the section of an occurrence of a fault on the basis of information on said polarity of each substation 1 and transmits said section as a fault section to said fault location identifying means 23c; 
said fault location identifying means 23c identifies the point of occurrence of a fault along the TD line on the basis of a difference in the time of detection of said surge detected by substations 1 at both ends of said fault section, and the length of said fault section along the TD line;
said TD line map information preparing means 23a identifies said point of occurrence of a fault along the TD line on a TD line of said TD line map information, re-prepares the TD line map information in consideration of said identified information at the point of occurrence of a fault as well, and transmits said re-prepared TD line map information to said TD line map information output means 24; and
said TD line map information output means 24 outputs said re-prepared TD line map information.
A fault point location system of a ninth embodiment in the fault point location system according to any one of embodiment 7 or 8, wherein said surge propagation velocity is 150 to 300 m/xcexcs.
Furthermore, said TD line map information can be prepared using a TD line map information preparing system described below. That is, a TD line map information preparing system comprises;
substations 1 which are installed along a TD line to transmit information on said TD line to a master station 2, and
a master station 2 which prepares information along TD lines on the basis of information from said substations 1; and may be such that
said substation 1 receives GPS radio waves from a satellite for identifying its own position on the basis of said GPS radio waves and then transmits information on said own position to said master station 2 via communication networks,
said master station 2 receives the information on the position of said substation 1 sent by said substation 1 via communication networks for preparing TD line map information which has TD lines illustrated on a map on the basis of map information on a region where each substation is installed and information on the position of said substations, and then outputs said TD line map information.
Furthermore, this TD line map information preparing system may comprise;
substations 1 which are installed along a TD line to transmit information on said TD line to a master station 2, and
a master station 2 which prepares information on TD lines on the basis of information from said substations 1.
Additionally, the map information storage means 22, in xe2x80x9cproviding map informationxe2x80x9d, may provide map information that is xe2x80x9cstoredxe2x80x9d therein for the TD line map information preparing means 23a, or map information stored in other storage means may be retrieved via a communication network and then provided for the TD line map information preparing means 23a. 
According to the foregoing TD line map information preparing system, TD line map information with TD lines illustrated on a map can be quickly re-prepared in response to relocation or extension of the TD line. Therefore, the latest TD line map information can always be provided.
A fault point location system of a tenth embodiment comprising;
substations 1 installed along TD lines for sending information on said TD lines to a master station 2, and
the master station 2 for locating fault points on the basis of the information sent by said substations 1;
characterized in that
said substation 1 has a clock function, receives radio waves from a GPS satellite to identify the current time of the GPS, is able to synchronize the current time of said GPS with the self current time, detects a surge current or surge voltage of the TD line on which said substation 1 is installed to identify a surge detection time, the time at which said surge current or surge voltage is detected, recognizes the polarity of said surge current, and then sends said surge detection time and information on said polarity to said master station 2 via a communication network; and
said master station 2 receives said surge detection time and information on said polarity, which are transmitted from said substation 1 via the communication network, identifies a potential point of an occurrence of a fault along the TD line on the basis of a difference in said surge detection time between said substation 1 which is the nearest to the source-side of said TD line and a plurality of distal end substations 1 of said TD line, and the length of the TD line between said substations 1 and 1, and totally identifies a predetermined range of a TD line with said potential point as a fault point potential section, and identifies a section with no branch as a section of an occurrence of a fault to determine a fault section on the basis of the information on polarities of a substation 1 within said fault point potential section and a substation 1, which is not included in said fault point potential section, adjacent to the substation 1 which is included in said fault point potential section.
In the foregoing, for example, determining the identified xe2x80x9csection with no branchxe2x80x9d not to be xe2x80x9ca fault sectionxe2x80x9d straightforwardly, but determining a section that is included both in the identified xe2x80x9csection with no branchxe2x80x9d and xe2x80x9cfault point potential sectionxe2x80x9d allows for confining a xe2x80x9cfault sectionxe2x80x9d by a narrower range.
The foregoing embodiment is valid particularly in the case where the xe2x80x9cpredetermined range with a potential pointxe2x80x9d provides a basis in selecting xe2x80x9ca fault point potential sectionxe2x80x9d.
A fault point location system of an eleventh embodiment has, in the fault point location system according to embodiment 10:
said substation 1 comprising a GPS receiving means 11, a time measuring means 12, a surge detection means 13, and a surge information transmitting means 14b, wherein
said GPS receiving means 11 receives GPS radio waves from satellites for identifying the current time of the GPS and sends the current time of said GPS to said time measuring means 12,
said time measuring means 12 has a clock function for synchronizing the current time of said GPS from said GPS receiving means 11 with the current time of said substation 1 and then sends information on said current time of said substation 1 to the surge detection means 13,
said surge detection means 13 detects a surge current or surge voltage of a TD line along which said substation 1 is installed, identifies the time of surge detection time at which said surge detection signal is received on the basis of information on the time sent by said time measuring means 12, also recognizes a polarity of said surge current, and transmits said surge detection time and said polarity to said surge information transmitting means 14b, and
said surge information transmitting means 14b sends said surge detection time and said information on polarity to said master station 2 via a communication network; and
said master station 2 comprising a substation surge information receiving means 21b, a fault point potential identifying means 23e, and a fault range confining means 23d, wherein
said substation surge information receiving means 21b receives said surge detection time sent by said surge information transmitting means 14b and said information on polarity via a communication network, then sends said surge detection time to said fault point potential identifying means 23e, and sends said information on polarity to said fault range confining means 23d, 
said fault point potential identifying means 23e identifies a potential point of occurrence of a fault along the TD line on the basis of a difference in said surge detection time between said substation 1 which is the nearest to the source-side end of said TD line and a plurality of distal end substations 1 of said TD line, and the length of the TD line between said substations 1 and 1, and totally identifies a predetermined range of a TD line with said potential point as a fault point potential section to be transmitted to said fault range confirming means 23d, 
said fault range confining means 23d identifies a section with no branch as a section of an occurrence of a fault to determine a fault section on the basis of the information on polarities of a substation 1 within said fault point potential section and a substation 1, which is not included in said fault point potential section, adjacent to the substation 1 which is included in said fault point potential section.
In the foregoing, assume the xe2x80x9cpolarityxe2x80x9d of a surge current xe2x80x9cpositive (+)xe2x80x9d for ground fault current flowing from a source-side to a load-side and xe2x80x9cnegative (xe2x88x92)xe2x80x9d for ground fault current flowing from the load-side to the source-side.
Additionally, the xe2x80x9csource-side endxe2x80x9d is an end that is connected to a source of a power station in a TD network. The xe2x80x9cdistal endxe2x80x9d is an end of a TD network, from which the TD line extends no further.
The xe2x80x9cpredetermined range with a potential pointxe2x80x9d can be determined, for example, according to the basis of errors conceivable for a predicted position of the xe2x80x9cpotential pointxe2x80x9d.
Furthermore, the number of xe2x80x9cpotential points of the an occurrence of a faultxe2x80x9d to be determined is equal to or greater than the number of xe2x80x9cdistal end substationsxe2x80x9d for which a difference in surge detection time has been discussed, thus being equal to the number of xe2x80x9cpredetermined ranges of the TD line with potential pointsxe2x80x9d. The fault point potential identifying means totals the TD lines to determine the fault point potential sections.
A fault point location system of a twelfth embodiment, according to embodiment 10 or 11, wherein said fault point potential identifying means 23e determines distance L1 along the TD line from said source-side end substation to the point of the fault on the TD line by equation L1=(L+(t1xe2x88x92t2)xc3x97v)/2, on the basis of said surge detection time t1 at the substation 1 nearest to the source-side end of said TD line, said surge detection time t2 at a distal end substation of said TD line, surge propagation velocity v, and length L of the TD line between said substations 1 and 1.
A fault point location system of a thirteenth embodiment, according to embodiment 11, wherein said fault point potential identifying means 23e determines distance L2 along the TD line from said distal end substation to the point of the fault along the TD line by equation L2=(L+(t1xe2x88x92t2)xc3x97v)/2, on the basis of said surge detection time t1 at the substation 1 nearest to the source-side end of said TD line, said surge detection time t2 at a distal end substation of said TD line, surge propagation velocity v, and length L of the TD line between said substations 1 and 1.
A fault point location system of a fourteenth embodiment, according to embodiment 11, wherein said fault range confining means:
1, selects one predetermined TD line from a group of TD lines among substations included within said fault location potential sections and substations that are not included within said fault point potential sections but adjacent to substations included within said fault point potential sections and are added to said fault point potential sections into a group of TD lines;
2. compares data of a surge rising polarity of a substation with that of its neighboring substation on said TD line selected;
3. selects one predetermined TD line from a group of TD lines among substations included within said fault point potential sections and substations that are not included within said fault point potential sections but adjacent to substations included within said fault point potential sections and are added to said fault point potential sections into a group of TD lines if there is no substation of a polarity opposite to the neighboring substation thereof to be replaced for said xe2x80x9cone TD line selectedxe2x80x9d and then performs from the procedure 2, and decides that there is no fault point if there is no TD line along which a fault section has not been checked;
4. if there is a substation of a polarity opposite to that of its neighboring substation and the section with these substations located at the ends of the section has no branch, identifies the section as a fault section;
5. if there is a substation of a polarity opposite to that of its neighboring substation and the section with these substations located at the ends of the section has a branch, compares the surge rising polarity data of the most upstream substation among the substations of the spur TD line with the surge rising polarity data of the upstream substation among substations which have a polarity opposite to that of their neighboring substation of the trunk TD line;
6. if there the polarity of the most upstream substation among the substations of said spur TD line is opposite to the polarity of the upstream substation among substations which have a polarity opposite to their neighboring substation of said trunk TD line, determines, to be a fault section, the section from the most upstream substation among the substations of said spur TD line through the upstream substation among substations which have a polarity opposite to their neighboring substation of said trunk TD line to the downstream substation among substations which have a polarity opposite to their neighboring substation of said trunk TD line; and
7. if there the polarity of the most upstream substation among the substations of said spur TD line is the same as the polarity of the upstream substation among substations which have a polarity opposite to their neighboring substation of said trunk TD line, selects one TD line from said spur TD lines to be replaced for said xe2x80x9cone TD line selectedxe2x80x9d and then performs the procedures from the foregoing procedure 2. In the foregoing, xe2x80x9cto select one TD linexe2x80x9d is defined as to select a series of TD lines with no branch out of TD lines with branches along the lines thereof, whereas defined as to select a TD line out of a TD line with no branch. In addition, the xe2x80x9cspur TD linexe2x80x9d is a TD line branched from xe2x80x9cone TD line selectedxe2x80x9d. The xe2x80x9ctrunk TD linexe2x80x9d is xe2x80x9cone TD line selectedxe2x80x9d. The xe2x80x9cspurxe2x80x9d and xe2x80x9ctrunkxe2x80x9d indicates, however, only a relative relationship of TD lines to be branched. Accordingly, the xe2x80x9ctrunk TD linexe2x80x9d is not always connected directly to a power station.
Moreover, the xe2x80x9cupstreamxe2x80x9d indicates source-side, while xe2x80x9cdownstreamxe2x80x9d indicates load-side.
A fault point location system according to any one of embodiments 12 through 14, is provided wherein said surge propagation velocity may be determined to be equal to 150 to 300 m/xcexcs. The above-mentioned allows a point of occurrence of a fault to be identified accurately on actual TD lines.
The fault point location system of the present invention can be the embodiment mentioned below.
That is, the master station 2 not only identifies a fault section but also prepares TD line map information according to information from substations 1 to display fault sections thereon.
A fault point location system of this embodiment is provided with said substation 1 comprising a GPS receiving means 11, a time measuring means 12, a surge detection means 13, a self-position information transmitting means 14a, and a surge information transmitting means 14b. 
Said master station 2 comprises a substation location information receiving means 21a, a substation surge information receiving means 21b, a map information storage means 22, a TD line map information preparing means 23a, a fault point potential identifying means 23e, a fault range confining means 23d, and TD line map information output means 24.
Furthermore, a fault point location system of this embodiment has components with the following functions for preparing TD line map information.
That is, said GPS receiving means 11 receives GPS radio waves from a satellite for identifying its own position on the basis of said GPS radio waves and then transmits information on said own position to said self-position information transmitting means 14a; 
said self-position information transmitting means 14a transmits information on said own position to said master station 2 via communication networks;
said substation location information receiving means 21 receives the information on the position of said substation 1 sent by said self-position information transmitting means 14a via communication networks to transmit the information on the position of said substation 1 to said TD line map information preparing means 23a; 
said map information storage means 22 is able to provide map information on a region where each substation is installed for said TD line map information preparing means 23a; 
said TD line map information preparing means 23a receives said map information from said map information storage means 22 for preparing TD line map information which has TD lines illustrated on a map on the basis of said map information and the information on the position of said substations which was received from said substation location information receiving means 21a to transmit said TD line map information to said TD line map information output means 24; and
said TD line map information output means 24 outputs said TD line map information.
Additionally, the map information storage means 22, in xe2x80x9cproviding map informationxe2x80x9d, may provide map information that is xe2x80x9cstoredxe2x80x9d therein for the TD line map information preparing means 23a, or map information stored in other storage means may be retrieved via a communication network and then provided for the TD line map information preparing means 23a. 
According to the foregoing TD line map information preparing system, TD line map information with TD lines illustrated on a map can be quickly re-prepared in response to relocation or extension of the TD line. Therefore, the latest TD line map information can always be provided.
Still furthermore, the fault point location system has components with the following functions for preparing TD line map information.
That is, said GPS receiving means 11 receives GPS radio waves from satellites for identifying the current time of the GPS and sends the current time said GPS has to said time measuring means 12,
said time measuring means 12 has a clock function for synchronizing the current time of said GPS from said GPS receiving means 11 with the current time of said substation 1 and then sends information on said current time of said substation 1 to the surge detection means 13,
said surge detection means 13 detects a surge current or surge voltage of a TD line along which said substation 1 is installed, identifies the time of surge detection time at which said surge detection signal is received on the basis of information on the time sent by said time measuring means 12, also recognizes a polarity of said surge current, and transmits said surge detection time and said polarity to said surge information transmitting means 14b, and
said surge information transmitting means 14b sends said surge detection time and said information on polarity to said master station 2 via a communication network.
Said substation surge information receiving means 21b receives said surge detection time sent by said surge information transmitting means 14b and said information on polarity via a communication network, then sends said surge detection time to said fault point potential identifying means 23e, and sends said information on polarity to said fault range confining means 23d, 
said fault point potential identifying means 23e identifies a potential point of occurrence of a fault along the TD line on the basis of a difference in said surge detection time between said substation 1 which is the nearest to the source-side end of said TD line and a plurality of distal substations 1 of said TD line, and the length of the TD line between said substations 1 and 1, and totally identifies a predetermined range of a TD line with said potential point as a fault point potential section to be transmitted to said fault range confining means 23d. 
Said fault range confining means 23d identifies a section with no branch as a section of an occurrence of a fault to determine a fault section on the basis of the information on polarities of a substation 1 within said fault point potential section and a substation, which is not included in said fault point potential section, adjacent to the substation 1 which is included in said fault point potential section;
said TD line map information preparing means 23a identifies said fault section of said TD line on a TD line of said TD line map information, re-prepares the TD line map information in consideration of said identified information at the point of occurrence of a fault as well, and transmits said re-prepared TD line map information to said TD line map information output means 24; and
said TD line map information output means 24 outputs said re-prepared TD line map information.
A fault point location system of the foregoing embodiment allows points of occurrence of a fault along TD lines to be displayed on the latest TD line map. Accordingly, maintenance personnel are able to rush to the spot of the fault point for quick recovery from the fault according to the TD line map prepared in accordance with the latest map.
According to the fault point location system of the first or the second embodiment, when a fault occurs along a TD line, the point of the fault can be quickly and accurately located.
According to the fault point location system of the third or the seventh embodiment, the point of occurrence of a fault along a TD line can be readily and effectively identified on the basis of a difference in surge detection time between both ends of the fault section.
According to the fault point location system of the fourth or the eighth embodiment, even when a fault occurs along a TD line with branches, the section with a fault point can be confined effectively to a section with no branch. Therefore, the fault point identifying method based on a difference in surge detection time between both ends of the fault section with no branch can be made available.
According to the fault point location system of the fifth or the sixth embodiment, when a fault occurs along a TD line, the location of the fault can be displayed on a TD line map prepared in accordance with the latest map. Accordingly, maintenance personnel are able to rush to the spot of the fault point for quick recovery from the fault according to the TD line map prepared in accordance with the latest map.
According to the fault point location system of the ninth embodiment, the point of occurrence of a fault on actual TD lines can be accurately identified.
The fault point location system of the tenth or eleventh embodiment allows, when a fault has occurred along a TD line, the fault point to be identified quickly and accurately.
According to the fault point location system of the twelfth or thirteenth embodiment, potential points of occurrence of a fault along a TD line can be identified readily and effectively on the basis of a difference in surge detection time between both ends of the fault section.
According to the fault point location system of the fourteenth embodiment, a fault section can be effectively located out of fault point potential sections determined according to a plurality of potential points.